EP3709928B1 - Method for virtually modeling a dental arch - Google Patents

Description

Field of invention

The invention relates to a method for virtual modeling of a dental arch, in which several overlapping images of the dental arch and a reference body are recorded from different angles and a virtual, three-dimensional dental arch model is calculated from the recorded images, with a partial impression of the dental arch as the reference body a patterned impression plate of known dimensions is used.

State of the art

Such a method is known from US 2016/000526 A1 .

In dentistry, especially oral surgery and dental prosthetics, exact dental arch models of patient's teeth are often required. The term dental arch is to be understood broadly in the present context and includes not only a complete arcus dentalis , but also parts of it. Likewise, the term refers both to the pure tooth arrangement and to the (toothed or toothless) tooth-bearing structures.

Physical dental arch models are often the basis for dental technical adaptation work that can be carried out extraorally in this way. Traditionally, physical arch models are created by molding the dental arch and pouring the resulting impression. However, virtual models are becoming increasingly important as a preliminary stage or even as an alternative to physical models.

For example, a virtual dental arch model can be used as the basis for 3D printing a physical dental arch model.

The basic technique for creating virtual, three-dimensional dental arch models is known to the person skilled in the art and is established and widespread in commercially available devices. A plurality of images of the dental arch to be modeled are recorded from different angles and the three-dimensional, virtual model is then calculated using established triangulation algorithms. The details of the algorithms used, the specific parameterization of the modeled surfaces as well as the storage and display formats, which are fundamentally known to the person skilled in the art, do not play a role in the context of the present invention.

In order to create virtual dental arch models, it is known, on the one hand, to map the dental arch itself intraorally. On the other hand, it is known to first produce a complete physical dental arch model and then to depict it extraorally. So reveals the already mentioned US 2016/000526 A1 the creation of virtual dental arch models of the upper and lower jaw of a patient on the basis of corresponding physical dental arch models in order to then determine correct relative occlusal positions of the jaws on the basis of the virtual models. A similar system is in the US 2007/190481 A1 disclosed. The disadvantage in both cases is that the interposition of a physical model results in a significant error potential. In this respect, it is therefore in principle more favorable to create a virtual model on the basis of a direct intraoral image of the dental arch.

Usually, however, the image field of the intraoral cameras used is relatively small, so that only a relatively small section of the object to be imaged can be recorded in each case. A very large number of images that overlap one another in areas are therefore typically recorded, which are then "superimposed" with their overlapping areas within the framework of the virtual modeling in order to generate a continuous image of the entire area of interest. This approach is commonly referred to as "stitching". Every single stitching process inevitably leads to minor errors, which are due, among other things, to the finite pixel size of the cameras used. One speaks here of so-called Registration errors. Especially when modeling large areas, for example a complete dental arch, these registration errors can add up to orders of magnitude of several 100 micrometers, so that certain dimensions of the virtual model, for example the distance between two opposing molars, deviate from the true dimensions to the extent mentioned. From a medical point of view, deviations of this magnitude cannot be tolerated as the basis for dental technical work, in particular for so-called circumferential dental technical work.

From the WO 03/100 729 A1 it is known to install reference bodies of precisely known dimensions on the dental arch to be modeled and to map these together with the dental arch and to model them virtually. The model can be corrected in such a way that the modeled dimensions of the reference bodies exactly correspond to their known, true dimensions, with a corresponding correction of the modeled dental arch dimensions taking place at the same time when using suitable inter- and extrapolation algorithms. The disadvantage of this system is the need to install said reference bodies intraorally, which makes the entire procedure complex and uncomfortable for the patient. The cited publication therefore proposes a modification of the method to completely mold the dental arch to be modeled in the usual way, pour the impression and install the reference body on the resulting physical model, which is then mapped and virtually modeled as a representative of the actual dental arch. However, this approach does not appear to be very effective, at least in those cases in which a physical model is dispensed with or a virtual model is to serve as the basis for a physical model. In addition, the reference bodies themselves are always included in the virtual model and must be subtracted afterwards. This leads to further inaccuracies, especially where an installed reference body hides structural details of the dental arch or the physical model.

An alternative is the one in the DE 10 2014 102 770 A1 disclosed approach. Here, too, it is necessary to have a complete imprint of the areas of interest in the registration of a bite fork. Instead of the dental arch itself or a physical model made on the basis of the impressions in the registration, in the context of this approach the impressions in the registration are recorded by means of a scanner and used as a basis of the virtual dental arch model to be calculated can be used. Of course, the problem of adding errors in "stitching" as outlined above basically exists here as well. This is countered in the cited publication in that the bite fork is equipped with clearly identifiable reference markings, the relative positions of which are known and can be referenced to the recorded partial images, which show both parts of the impressions and parts of the markings. In addition, the cited publication also discloses the possibility of attaching further absolute position markers to the bite fork, which allow the position of the bite fork to be determined relative to an absolute coordinate system at the time the impressions are made in the registration, ie when the patient bites into the registration of the bites , relative to which the patient's head is also positioned in a known (because it is measured) manner. In this way it is possible to reference the virtual model to the absolute coordinate system and therefore to special anatomical features on the patient's head. This is of particular importance if dynamic processes, such as the relative movement of the upper and lower jaw, are to be simulated. However, this possibility does not play a role in the context of the present invention.

Also the DE 20 2015 105 356 U1 and the DE 10 2011 005 802 A1 pursue fundamentally similar approaches in which only the impressions in the registration of a bite fork are scanned for images. Also the US 2005/0153257 1 discloses a similar system. These approaches have the disadvantage that the accuracy of the virtual model suffers from the fact that it is not the object of interest as such, i.e. the dental arch itself, but a possibly incorrectly created representative object, namely the impressions in the registry, that is scanned and used as the basis of the virtual model is used.

the WO 2016/110855 A1 discloses a method with the aim of creating a (final) virtual dental arch model by correcting a preliminary virtual dental arch model on the basis of a virtual reference model. The preliminary dental arch model is calculated on the basis of a first intraoral scan. The reference model is determined on the basis of a second intraoral scan in which a fiducial marker with known dimensions is applied to corresponding structures of the dental arch and scanned together with it. From the familiarity of the marker positions, the true relative positions of the scanned, corresponding dental arch structures are closed. These are then identified in the preliminary dental arch model and the entire preliminary dental arch model is corrected in such a way that said corresponding dental arch structures assume the said true relative positions with respect to one another. The disadvantage is the high stress on the patient, namely in particular with two intraoral scans and the temporary fixation of the fiducial marker. on the dental arch.

Task

The object of the present invention is to make a generic method for virtual modeling of a dental arch more precise and less uncomfortable for the patient.

Statement of the invention

• aus intraoral aufgenommenen Bildern des Zahnbogens ein virtuelles dreidimensionales vorläufiges Zahnbogenmodell berechnet wird,
• aus extraoral aufgenommenen Bildern des Referenzkörpers ein virtuelles, dreidimensionales Referenzmodell berechnet wird und
• zur Schaffung des Zahnbogenmodells die Dimensionen des vorläufigen Zahnbogenmodells korrigiert werden anhand von im Referenzmodell realisierten Dimensionen solcher Strukturmerkmale, die sowohl im vorläufigen Zahnbogenmodell als auch im Referenzmodell vorhanden sind.

This object is achieved in connection with the features of the preamble of claim 1 in that

• A virtual three-dimensional preliminary dental arch model is calculated from intraorally recorded images of the dental arch,
• A virtual, three-dimensional reference model is calculated from extraorally recorded images of the reference body, and
• To create the dental arch model, the dimensions of the preliminary dental arch model are corrected on the basis of the dimensions of structural features realized in the reference model that are present both in the preliminary dental arch model and in the reference model.

Preferred embodiments of the invention are the subject of the dependent claims.

The basic idea of the invention is to spatially (and preferably also temporally) separate the mapping of the dental arch, on the one hand, and the reference body, which is necessary for the virtual modeling.

The imaging of the dental arch takes place intraorally. The object to be modeled is thus mapped directly itself, which excludes errors that could occur in the context of intermediate steps. On the other hand, imaging the dental arch by means of an intraoral camera is a minimally invasive procedure that is not very unpleasant for the patient.

The image of the reference body, on the other hand, takes place extraorally. In particular, it is not necessary to fix the reference body on the dental arch itself. The exact dimensions of the reference body result from the pattern of the impression plate known (in terms of its dimensions). The pattern is preferably non-periodic, so that each pattern section imaged on any image of a partial area of the reference body can be clearly identified. Familiarity with the impression plate or its pattern means in particular that the distance between each pattern section and every other pattern section is known or can be determined from known information. If, because of the non-periodicity, all of the mapped pattern sections can be clearly identified and thus localized, then their distances from one another and thus the distances between the adjacent areas of the partial impression mapped together with the pattern can also be determined.

In principle, it is also possible to use a periodic pattern. Then, however, the entire impression plate should be mapped when the reference body is mapped so that each individual pattern position can be clearly identified - quasi by "counting" the periods, starting from an identifiable starting point. In the case of the preferred use of a non-periodic pattern, on the other hand, it may be sufficient to depict isolated sections of the impression plate. This advantage has a particularly advantageous effect, in particular in the case of embodiments described in more detail below, in which the partial impression also only comprises isolated areas.

The images of the partial impression on the impression plate in turn form the interface with the images of the actual dental arch, since they represent the exact negative of certain partial areas of the dental arch. In the images of the dental arch it is therefore possible to identify those areas which are represented in the reference body by the partial impression and whose distances from one another can be precisely determined on the basis of the pattern. These precisely determined distances can then be transferred to the virtual dental arch model, so that registration errors that occur during its Calculation have occurred can be corrected. At the same time, it is not necessary to make a full impression of the dental arch, which is unpleasant for the patient and requires great technical ability. Rather, the simple production of a flat partial impression, which is easy on the patient, is sufficient, for example with a scannable bite registration material.

The method according to the invention therefore provides a particularly high dimensional accuracy of the virtual model, in particular a correction (or - included in this term, an avoidance) of registration errors and at the same time minimizes the burden on the patient.

• aus den intraoral aufgenommenen Bildern des Zahnbogens ein virtuelles, dreidimensionales vorläufiges Zahnbogenmodell berechnet wird,
• aus den extraoral aufgenommenen Bildern des Referenzkörpers - vorzugsweise unter räumlicher Invertierung - ein virtuelles, dreidimensionales Referenzmodell berechnet wird und
• zur Schaffung des (endgültigen) Zahnbogenmodells die Dimensionen des vorläufigen Zahnbogenmodells korrigiert werden anhand von im Referenzmodell realisierten Dimensionen solcher Strukturmerkmale, die sowohl im vorläufigen Zahnbogenmodell als auch im Referenzmodell vorhanden sind.

In a preferred embodiment, the method according to the invention is carried out in detail by

• a virtual, three-dimensional preliminary dental arch model is calculated from the intraorally recorded images of the dental arch,
• a virtual, three-dimensional reference model is calculated from the extraorally recorded images of the reference body - preferably with spatial inversion - and
• To create the (final) dental arch model, the dimensions of the preliminary dental arch model are corrected on the basis of the dimensions of structural features realized in the reference model that are present both in the preliminary dental arch model and in the reference model.

In other words, a preliminary dental arch model (namely based on the intraorally recorded dental arch images) and a reference model (based on the extraorally recorded reference body images) are initially calculated independently of one another. The preliminary dental arch model contains all structural details of the dental arch, but at the same time the registration error explained above. The reference model, however, is dimensionally correct; however, it contains only a few structural details. In a correction step, both models are virtually “superimposed”, the preliminary dental arch model being compressed, stretched and / or twisted in such a way that the structural details contained in both models match precisely in position and orientation. It can then be assumed that the points between these support points and only in the preliminary Structural details contained in the dental arch model are also correctly positioned and oriented. The resulting, final dental arch model is characterized by a particularly high level of detail and a particularly high degree of dimensional accuracy.

• aus den Bildern des Referenzkörpers zunächst ein vorläufiges Referenzmodell berechnet wird und
• zur Schaffung des (endgültigen) Referenzmodells die Dimensionen des vorläufigen Referenzmodells korrigiert werden anhand von in einem hinterlegten, virtuellen, dreidimensionalen Plattenmodell der Abdruckplatte realisierten Dimensionen solcher Mustermerkmale, die sowohl im vorläufigen Referenzmodel als auch im Plattenmodell vorhanden sind.

As mentioned, the reference model contains the required, precise dimensional information, namely on the basis of the precisely known pattern on the impression plate. The dimensions of the partial impression, on the other hand, on which, as explained above, the actual correction of the preliminary dental arch model is based, are not known a priori. In particular, the calculation of a model of the reference body is subject to the same registration errors as the calculation of a model of any other body, in particular the dental arch. In order to arrive at a reference model with precisely known dimensions of the partial imprint that can be used within the scope of the method according to the invention, different ways are conceivable. It is preferably provided that

• a preliminary reference model is first calculated from the images of the reference body and
• To create the (final) reference model, the dimensions of the preliminary reference model are corrected on the basis of the dimensions of such pattern features, which are present in both the preliminary reference model and the plate model, in a stored, virtual, three-dimensional plate model of the impression plate.

In other words, two models are first calculated here as well. The preliminary reference model is subject to registration error; However, it contains all structural details of the partial impression and the impression plate, in particular its pattern. The plate model of the impression plate, on the other hand, is not subject to any registration errors. For example, it can be based on a precision measurement carried out with special measuring machines. However, it does not contain any structural information about the partial impression, but only the (dimensionally accurate) structural details of the impression plate, in particular its pattern. In a correction step, the two models are then "placed one on top of the other", the preliminary reference model being compressed, stretched and / or twisted in such a way that the pattern details contained therein match the pattern details of the plate model precisely. It can then be expected that the structural details of the Structures not contained in the plate model, ie in particular the structures of the partial impression, are also precisely positioned and oriented. This corrected model can then be used as the (final) reference model for the correction of the preliminary dental arch model explained above.

As explained, the non-periodicity of the pattern on the impression plate is favorable for the efficiency of the method according to the invention. In a particularly advantageous embodiment, the pattern of the impression plate even consists of randomly distributed pattern elements. In particular, it is not necessary to design the pattern according to some kind of (non-periodic) scheme. Precise knowledge of the realized pattern is essential, but not knowledge of the way in which it was created. Nevertheless, such additional information can be used via a generation scheme, for example for the definition of the plate model explained above, which, if the production scheme is known, can also be generated in a purely theoretical way without the above-mentioned precision measurement.

The pattern of the impression plate is advantageously designed as a relief. With this approach, the modeling algorithms do not have to differentiate qualitatively between pattern details and partial imprint details. The calculations required in the context of the modeling are therefore simpler than in - quite feasible - cases in which the pattern is of a purely optical nature.

In the context of a relief-like pattern, it has proven to be particularly advantageous if the relief has spherical segments of different radii and / or different heights. Spherical segments are pattern elements that can be produced easily and that in particular do not contain any undercuts or mutual coverings, so that their image acquisition and their virtual modeling can be carried out particularly easily and without gaps. With the parameters "Segment height" and "Radius", two additional criteria are available for the pattern generation with clearly localizable pattern sections.

The partial impression on the impression plate preferably consists of a plurality of simultaneously molded partial impression elements arranged in isolation on the impression plate. These partial imprint elements serve as support points for subsequent calculations. Between however, the impression plate and in particular its pattern for the image recording remain recognizable to them. The more structural details of the partial imprint elements in the immediate vicinity of structural details of the pattern can be mapped together on one image, the more precisely the position and orientation of the structural details of the partial imprint elements can be modeled, ie the more precise the reference model.

As already mentioned above, the production of the reference body can be done very easily and with little stress on the patient. It is preferably provided that, in order to produce the reference body, an impression body comprising the impression plate covered in areas with deformable impression material is pressed from the occlusal direction against the dental arch. In particular, it is considered favorable if the impression body is formed from the impression plate covered with the isolated portions of deformable impression material. This procedure essentially corresponds to the traditional impression taking of dental arches, but differs from this in the significantly reduced use of impression material. Small portions of impression material are only distributed on the impression plate at a few isolated positions and this impression body is briefly pressed onto the dental arch. In contrast to a complete impression, this partial impression can be done quickly and easily by hand and, due to the significantly reduced volume compared to a traditional impression tray, does not lead to unpleasant side effects such as choking etc. in the patient.

The user of the method according to the invention is largely free to choose the specific impression material. It is conceivable to use a hardening impression material and to allow it to harden before the images of the reference body are recorded. During hardening, however, undesirable shrinkage and thus dimensional errors can occur. Since the partial impression within the scope of the method according to the invention, however, is not exposed to any mechanical stress, but is reproduced purely optically, it is also possible to use a permanently elastic impression compound. After the method according to the invention has been carried out, this can generally also be removed more easily from the impression plate, which is then available for the production of a new reference body.

Further features and advantages of the invention emerge from the following specific description and the drawings.

Brief description of the drawings

Figur 1:

einen ersten Schritt einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens,

Figur 2:

einen zweiten Schritt einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens,

Figur 3:

einen dritten Schritt einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens,

Figur 4:

einen vierten Schritt einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens,

Figur 5:

einen fünften Schritt einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens,

Figur 6:

einen sechsten Schritt einer bevorzugten Ausführungsform des erfindungsgemäßen Verfahrens,

Figur 7:

einen ersten Schritt einer besonders vorteilhaften Weiterbildung des erfindungsgemäßen Verfahrens,

Figur 8:

einen zweiten Schritt einer besonders vorteilhaften Weiterbildung des erfindungsgemäßen Verfahrens sowie

Figur 9:

einen dritten Schritt einer besonders vorteilhaften Weiterbildung des erfindungsgemäßen Verfahrens.

Show it:

Figure 1:

a first step of a preferred embodiment of the method according to the invention,

Figure 2:

a second step of a preferred embodiment of the method according to the invention,

Figure 3:

a third step of a preferred embodiment of the method according to the invention,

Figure 4:

a fourth step of a preferred embodiment of the method according to the invention,

Figure 5:

a fifth step of a preferred embodiment of the method according to the invention,

Figure 6:

a sixth step of a preferred embodiment of the method according to the invention,

Figure 7:

a first step of a particularly advantageous development of the method according to the invention,

Figure 8:

a second step of a particularly advantageous development of the method according to the invention and

Figure 9:

a third step of a particularly advantageous development of the method according to the invention.

Description of preferred embodiments

Identical reference symbols in the figures indicate identical or analogous elements.

the Figures 1 to 6 show an advantageous embodiment of a method according to the invention for virtual modeling of a dental arch 10. In partial FIG. 1 a, the dental arch 10 is shown in isolation. However, this is solely for the sake of clarity of the drawings. The method according to the invention relates in particular to the modeling of a dental arch 10 in situ. Partial figure 1b shows an impression body 20 as it is preferably used in the context of the method according to the invention. The impression body 20 consists of an impression plate 22 which bears a non-periodic, relief-like pattern, which preferably consists of statistically distributed pattern elements, particularly preferably of spherical segments of different radii and / or different heights. A plurality of portions 24 of deformable molding compound - four in partial FIG. 1b - are positioned isolated from one another on the molding plate 22. A handle 26 on the impression plate 22 facilitates the handling of the impression body 20.

As in Figure 2 indicated, the impression body 20 is pressed from the coronal direction onto the dental arch 10 and lifted off again.

At the beginning of the actual modeling process, as in Figure 3 shown, the dental arch 10 to be modeled (partial figure 1a) and a reference body 30 (partial figure 1b) are available. The latter essentially comprises the impression plate 22 and a partial impression 32 of the dental arch 10, the partial impression 32 representing the negative of the dental arch 10 in those areas in which the impression compound 24 is taken during the molding step of Figure 2 was in contact with the dental arch 10.

In the following, in Figure 4 In the step shown, overlapping images of the dental arch 10 are recorded from different viewing directions by means of an intraoral camera 40. From this, a three-dimensional, virtual model of the dental arch 10 is calculated in the usual way, preferably by “stitching”, which is referred to here as the preliminary dental arch model 100. The preliminary dental arch model 100 contains the registration errors that are inevitable in such modeling processes.

In the in Figure 5 step shown before, after or at the same time as the one in Figure 4 can be performed, the reference body 30 is imaged by means of an extraoral camera 42. The extraoral camera 42 can be the same device as the intraoral camera 40, but being used intraorally in one case and extraorally in the other. Here, too, a large number of overlapping images are recorded from different viewing directions. In particular, both the partial impression 32 and the pattern of the impression plate 22 are recorded. The pattern of the impression plate 22 is known in detail. Therefore, a reference model 300, which is calculated from the recorded images of the reference body 30, can be designed with exact dimensions.

In the in Figure 6 In the final step shown, the preliminary dental arch model 100 is then corrected by comparison with the reference model 300. In particular, the preliminary dental arch model 100 is computationally compressed, stretched and / or twisted in such a way that areas of the preliminary dental arch model 100 that have partial impression areas of the reference model 300 correspond to the latter in terms of their position and orientation. In this way, the registration error in the preliminary dental arch model 100 can be corrected and a final dental arch model with exact dimensions (not shown separately in the figures) can be generated. This can then be the basis for further dental or dental technical measures. For example, it can be used for the 3D printing of a dimensionally accurate physical dental arch model, on which even circumferential dentures can then be precisely manufactured. Alternatively, the dimensionally accurate virtual dental arch model can be used directly for the production of (circumferential) dentures.

the Figures 7 to 9 outline particularly preferred steps for creating the dimensionally accurate reference model 30. As in Figure 7 For this purpose, the reference body 30 is imaged by means of an extraoral camera 42 and a preliminary reference model 310 is calculated therefrom using conventional modeling methods. This preliminary reference model 310 is still subject to the registration error which is unavoidable in conventional modeling methods.

According to Figure 8 however, an exact plate model 400 of the impression plate 22 is provided. This can be created using a precision measuring machine that does not generate any noteworthy registration errors. Such precision measuring machines are known to the person skilled in the art. In particular, by taking very large images that depict the entire impression plate 22 and can dispense with “stitching”, the registration error can be avoided. However, such precision measuring machines are expensive and highly complex to operate and are typically not available in dental or dental technology laboratories. The patterned impression plates used when carrying out the method according to the invention should therefore preferably already be measured by the manufacturer and delivered together with a data record representing the dimensionally accurate plate model 400.

Analogous to the comparison step of Figure 5 can then, as in Figure 9 shown, a comparison of the preliminary reference model 310 with the dimensionally accurate plate model 400 take place. The preliminary reference model 310 is compressed, stretched and / or twisted in such a way that the pattern areas modeled in both models match exactly. In this way, the final reference model 300 is generated, which is used as the dimensionally accurate reference model 300 in the comparison step of FIG Figure 6 can be used.

Of course, the embodiments discussed in the specific description and shown in the figures represent only illustrative embodiments of the present invention. In the light of the disclosure here, a person skilled in the art is provided with a broad spectrum of possible variations. In particular, the functional process stages described here as individual steps can be carried out at least partially together when using suitable algorithms.

List of reference symbols

10

Dental arch

20th

Impression body

22nd

Impression plate

24

Servings of impression material

26th

Handle

30th

Reference body

32

Partial print

40

Intraoral camera

42

Extraoral camera

100

preliminary dental arch model

300

Reference model

310

preliminary reference model

400

Plate model

Claims (9)

1. A method for virtually modeling a dental arch (10), wherein a plurality of overlapping images of the dental arch (10) and of a reference body (30) is captured from different angles of view and a virtual, three-dimensional dental arch model is computed from the captured images,
   wherein a partial impression (32) of the dental arch (10) on an impression plate (22) of known dimensions is used as the reference body (30), which impression plate is provided with a pattern.
   characterized in that

   - a virtual, three-dimensional, preliminary dental arch model (100) is computed from images of the dental arch (10) captured intraorally,

   - a virtual, three-dimensional reference model (300) is computed from images of the reference body (30) captured extraorally, and

   - to create the dental arch model, the dimensions of the preliminary dental arch model (100) are corrected based on the dimensions of those structural features, realized in the reference model (300), which are present both in the preliminary dental arch model (100) as well as in the reference model (300).
2. The method according to claim 1,
   characterized in that
   the pattern is a non-periodic pattern.
3. The method according to any one of the preceding claims,
   characterized in that

   - a preliminary reference model (310) is first computed from the images of the reference body (30), and

   - to create the reference model (300), the dimensions of the preliminary reference model (310) are corrected based on realized dimensions of those pattern features from a saved, virtual, three-dimensional plate model (400) of the impression plate (22) that are present in both the preliminary reference model (310) as well as in the plate model (400).
4. The method according to any one of the preceding claims,
   characterized in that
   the pattern of the impression plate (22) is composed of statistically distributed pattern elements.
5. The method according to any one of the preceding claims,
   characterized in that
   the pattern of the impression plate (22) is structured as a relief.
6. The method according to claim 5,
   characterized in that
   the relief has ball segments of differing radii and/or differing heights.
7. The method according to any one of the preceding claims,
   characterized in that
   the partial impression (32) is composed of a plurality of simultaneously impressed partial impression elements that are arranged in isolated fashion on the impression plate.
8. The method according to any one of the preceding claims,
   characterized in that,
   to produce the reference body (30), an impression body (20) comprising the impression plate (22) with deformable impression material (24) arranged in sections is pressed against the dental arch (10) from the occlusal direction.
9. The method according to claim 8,
   characterized in that
   the impression body (20) comprises the impression plate (22) which is laden with portions of deformable impression material (24) arranged in isolated fashion.

Images